This invention relates to accurately shaped artificial, all ceramic tooth crowns for dental prosthetic constructions. By starting from a prefabricated coping, a tooth crown is obtained which is easier to produce and therefore of lower cost. In addition, the crown has higher strength and a more accurate shape. Preferably the coping is manufactured from a biocompatible, high strength, ceramic material, which is sintered to high density.
U.S. Pat. No. 4,575,340 describes a prefabricated abutment used in combination with a prefabricated sleeve-like coping telescopically mated to the abutment. This coping is made by a known lost-wax method of a precious or non-precious metal.
Artificial tooth crowns are today manufactured mainly in the following way: A dentist makes a preparation on a tooth, on which a tooth crown is to be fixed in the mouth of a patient, an impression is made and with this impression a copy of the preparation is made in gypsum. On this model, a dental technician prepares a crown of wax. The adjacent teeth must be considered, and the dental technician must have models from the two jaws. A sprue former in wax is fixed on one of the cusps of the wax crown. The wax crown is loosened from the gypsum model. The wax crown with the sprue former are invested in a metal ring with investment. The wax is burnt out and a crown can be cast in a precious or non-precious metal. The cast crown can, in certain cases, be covered by a veneer made of porcelain in order to obtain a tooth crown color similar to the color of natural teeth. Instead of porcelain, plastic material can be used.
The fabrication of tooth crowns in glass is very close to the technique described above with the difference that after the casting, a thin layer of porcelain is painted on the surface and fired in order to give the tooth crown individual tooth colors.
Tooth crowns fabricated mainly of porcelain can be made with conventional dental porcelain technique from a sheet made of a precious or non-precious alloy. Porcelain crowns can also be made with conventional dental porcelain technique on a model of the abutment. The material of this model does not change dimensions on heating up to 1200.degree. C. When the tooth crown is ready the model of the abutment is removed by sand blasting.
The above described complicated and time consuming methods are today used to manufacture crowns, which will fit on individually prepared natural teeth, on prefabricated abutments for implants, and on prefabricated pins for anchoring of tooth crowns to root filled teeth.
The problem with the material now used (porcelain, glass, etc.) in artificial tooth crowns is their brittleness, which often leads to early fracture. These artificial crowns must be replaced more or less regularly.